Mulch Volcanoes
The grass was manicured, the shrubs were pruned and the borders were weeded and newly mulched. Obviously someone cared about this landscape. Only one thing marred the scene.
Mulching trees is good. Mulch volcanoes are not.
The deep cones of mulch cause damage to the roots and the bark of the tree. Tree roots lie close to the surface of the soil, seeking nutrients, water and oxygen. The roots of newly-planted trees are contained in the root-ball and they are the trees most often emerging from mulch volcanoes. Newly planted trees are dependent on moisture in the original root-ball until the roots grow into the surrounding soil.
Water runs off the cones when the surface becomes sealed by fungal growth or the settling of fine particles. This places the water beyond the reach of the roots.
Mulch in contact with the bark of the tree promotes fungal cankers caused by constant moisture around trunk. It also encourages damage by rodents. Hidden from predators, mice and voles eat the cambium layer of the tree.
A walk in a forest provides an example of how to mulch trees. The forest litter is not piled in cones around the base of the trees. It is spread in an even layer on the forest floor. Here are a few suggests to help properly mulch your trees.
Spread an even layer of mulch two to four inches deep in a circle around the tree. Ideally the mulch layer would extent to the drip-line of the tree. When mulch is more than four inches deep roots tend to migrate up into it during rainy periods or when irrigation temporarily causes favorable conditions. Excessively deep layers of mulch can become water-logged, suffocating deep roots. Roots require oxygen to function properly.
Do not use plastic sheeting under mulch. The plastic sheeting does not allow water to penetrate to the root zone. It also may inhibit the passage of oxygen to roots.
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